Apparatus for varying electroplating current

ABSTRACT

In accordance with certain of its aspects, the apparatus of this invention provides for the electrodeposition of metals onto basis materials, with the basis materials, because of diversity in size and shape, exhibiting differing electrical current characteristics requiring various optimum currents, and having a supporting frame and extending laterally therefrom and a work-supporting rack mounted on the arm and extending downwardly therefrom into a treating vessel. A workpiece of particular size and shape is mounted on the work-supporting rack; a calibrated mechanical variator may be mounted on either the lateral arm or the work-supporting rack and is pre-set in accordance with the desired treating current for the particular workpiece being processed. An electrical signaler is established bias to said variator and includes a variable resistance the value of which is determined by the setting of the variator noted above. A variable current source is provided the output of which is determined by the value of the resistance of the electrical signaler. In addition, flow communication means conveys the desired treating current from the current source to the workpiece being processed so that the current passing through the work-supporting rack and the workpiece yields plating current density over the surface of the said workpiece.

APPARATUS FOR VARYING ELECTROPLATING CURRENT Filed Jan. 2, 1969 3 Sheets-Sheet l H. CHESSIN 3,632,499

APPARATUS FOR VARYING ELECTROPLATING CURRENT Jan. 4, 1972 3 Sheets-Sheet 2 Filed Jan.

APPARATUS FOR VARYING ELECTROPLATING CURRENT Filed Jan. 2, 1969 H. CHESSIN Jan. 4, 1972 3 Sheets-Sheet I5 United States Patent 3,632,499 APPARATUS FOR VARYING ELECTROPLATING CURRENT Hyman Chessin, Birmingham, Mich., assignor to M & T Chemicals Inc., New York, N.Y. Filed Jan. 2, 1969, Ser. No. 788,367 Int. Cl. C23b 5/70 US. Cl. 204-297 R 5 Claims ABSTRACT OF THE DISCLOSURE In accordance with certain of its aspects, the apparatus of this invention provides for the electrodeposition of metals onto basis materials, with the basis materials, because of diversity in size and shape, exhibiting difiering electrical current characteristics requiring various optimum currents, and having a supporting frame, at least one arm mounted on the supporting frame and extending laterally therefrom and a work-supporting rack mounted on the arm and extending downwardly therefrom into a treating vessel. A workpiece of particular size and shape is mounted on the work-supporting rack; a calibrated mechanical variator may be mounted on either the lateral arm or the work-supporting rack and is pre-set in accordance with the desired treating current for the particular workpiece being processed. An electrical signaler is established bias to said variator and includes a variable resistance the value of which is determined by the setting of the variator noted above. A variable current source is provided the output of which is determined by the value of the resistance of the electrical signaler. In addition, flow communication means conveys the desired treating current from the current source to the workpiece being processed so that the current passing through the worksupporting rack and the workpiece yields plating current density over the surface of the said workpiece.

This invention relates to novel apparatus for use in electrodeposition of metals onto basis materials, and particularly where the basis materials, because of diversity in size and shape, exhibit difiering electrical current characteristics requiring various optimum currents for the attainment of an acceptable metal deposition surface.

In the electrodeposition of metals upon various objects to be plated, which are carried by a plating or work rack to the various treatment tanks, certain optimum currents are required for acceptable plate. For the electrodeposition of metals upon these various objects, a lesser amount of current may be required for objects of small area, while objects of larger area usually require higher current. The configuration of the object being plated may influence the amount of current required also. For example, objects with sharp corners generally require less average current density to avoid burning in these sharp corners. Objects with deep recesses may require higher average current density suflicient to electrodeposit in the recessed area. In practice, the optimum current may be the highest usable current, one just insuflicient to cause unsightly burning in the highest current density areas.

Usually, the only in rare cases is just one kind of object continuously plated. In the usual plating line, a variety of objects and a variety of rack loads are processed. In many of these cases, attempts have been made to equalize the plating areas and to kee identical rack loads together in sequence but balancing areas of the objects to be plated as discussed above has met with little success since area alone is usually not the sole criterion.

As is well known, each plating rack loaded with objects to be plated may have an optimum current which must be empirically determined for each rack in order to obtain a successful plate. In the past, the plating current has been only partially controlled, and this only with constant supervision by an attendant. Such supervision is expensive and usually meets with only limited success. Further, as well understood, certain time limitations are apparent when utilizing prior art apparatus in fully automatic plating operations.

In many electrodeposition systems, attempts have been made to obtain optimum current for successful electrodeposition of metals for regulating the current source through the use of rectifiers which provide an average current necessary to obtain a proper and acceptable electrodeposition upon the objects placed in the various plating tanks employed therewith. This is at best an average current for these objects which may dilfer greatly in size, weight, area and physical configuration, and therefore, the optimum current for an individual object may never be approached.

The conventional type of plating line may contain various treatments tanks, including alkaline cleaners, and dips, water rinses, etc., and various electrodeposition treatment tanks, including aqueous copper solutions, nickel solutions, chromium solutions, etc. In this conventional type plating line, horizontal conveying apparatus may be employed to convey the various racks of objects to be plated from one treatment tank to another. Upon this horizontal conveying means, a side arm is affixed. This side arm is the means by which the plating rack may be moved, and is electrified with the objects to be plated racked upon a work or plating rack and hung upon the arms. Bus bars are provided for supplying current to the arms when they are in the down position with the rack immersed in the treatment tank. The usual source of energy for the bus bar may be a silicon controlled rectifier, a saturable core reactor type or a motor-generator set.

By contrast, the present invention provides for a variable control element to be permanently aflixed to each arm of a plating conveyor. This control element determines the magnitude of current which is to be applied to the particular work rack suspended on its arm. One object of this invention, therefore, is then the individual suspending the rack onto the arm sets the value of the calibrated variable control element to that value corresponding to the desired current previously determined to be optimum. The control elements may also be attached to the individual racks rather than to the arms of the plating conveyor. Thus the particular optimum currents peculiar to the particular rack, because of the area and configuration of the work pieces thereon, are pro-determined when the control element is pre-set. In those cases where the control element is afiixed to the work rack, the value-setting of this element is accomplished by the individual racking the work pieces or by the individual suspending the work rack onto the arm of the plating conveyor. In those cases where racks are constructed for a specific load, the control element need not be variable and is usually pre-set to the pre-determined optimum value in construction.

The control element is comprised of an electrical signaler such as a variable resistance bias to a calibrated mechanical variator, and may be a rheostat with a numbered or indexed dial, a set of resistances controlled by push buttons, or a slide wiping over a resistance element having an indexed setting for controlling current. The output of the current source to the individual work rack is determined by the control element.

In accordance with certain of its aspects, the apparatus of this invention provides for the electro-deposition of metals onto basis materials, with the basis materials, because of diversity in size and shape exhibiting differing electrical current characteristics requiring various optimum currents, and having a supporting frame, at least one arm mounted on the supporting frame and extending laterally therefrom and a work-supporting rack mounted on the arm and extending downwardly therefrom into a treating vessel. A workpiece of particular size and shape is mounted on the work-supporting rack; a calibrated mechanical variator may be mounted on either the lateral arm or the work-supporting rack and is pre-set in accordance with the desired treating current for the particular workpiece being processed. An electrical signaler is established bias to said variator and includes a variable resistance the value of which is determined by the setting of the variator noted above. A variable current source is provided the output of which is determined by the value of the resistance of the electrical signaler. In addition, flow communication means conveys the desired treating current from the current source to the workpiece being processed so that the current passing through the worksupporting rack and the workpiece yields plating current density over the surface of the said workpiece.

Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings, and the appended claims.

Ln the drawings:

FIG. 1 is a fragmentary perspective view of a work carrying arm, mounted upon a suitable supporting frame of an electrodeposition processing machine and including mechanical aspects of apparatus embodying and for practising the invention;

FIG. 2 is an electrical schematic of the aligned microswitches and the electrical equivalents which form the current density variation of FIG. 1;

FIG. 3 is a fragmentary perspective view of a Work rack embodying a further modification of apparatus for practising this invention and including the mechanical current density variator applied thereon;

FIG. 4 is a schematic indication of the aligned microswitches at a treatment station of an electrodeposition processing machine embodying and for practising this invention;

FIG. 5 is a fragmentary perspective view of a. work arm embodying a further modification of apparatus for practising this invention, and showing the mechanical variator and the electrical signaler mounted thereon;

FIG. 6 is an enlarged electrical schematic indication of the current density variator shown in FIG. 5

FIG. 7 is an enlarged front elevational view of the dial indicator employed with the form of current density variator shown in FIG. 5.

Referring to the drawings, in which like characters refer to like parts throughout the several views thereof, FIG. 1 shows a side arm bus bar 10 mounted on a vertical slide 11, as well understood, which permits the arm 10 to be raised and lowered over various treatment stations or treating tanks, not shown, for depositing a Work rack 12 into electrochemical solutions in the treatment tanks, in well known manner, which rack 12 has a hanger 14 which engages an electrified support 15 on the side arm 10. The electrified support 15 is fed through the side arm bus bar 10 and is in communication with collectors 16 and 18 which engage bus bars, not shown, supported by the electroplating machine. A coliar 19 mounted on the side arm bus bar 10' supports a pin retaining plate 20. Pins 21 are ailixed to the pin retaining plate 20.

As best seen in FIG. 2, a plurality of micro-switches 22 located at the treatment station are aligned with pins 21 as seen in FIG. 1. A schematic electrical equivalent 24 of the aligned micro-switches 22 are shown in an open position. As one or more of pins 21'depress the aligned micro-switches 22, circuit 24 is completed, for shorting out a portion of the resistors 25 for changing the magnitude of the total resistance of resistors 25. The total resistance of resistors 25 communicates through the terminals 26 and 28 to a variable current source not shown, thereby controlling the output of total current.

Referring now to FIGS. 3 and 4, wherein the work rack 29 is shown as being similar to Work rack 12 in FIG. 1 and having a neck portion 30 and a hanger portion 31. The hanger 31 likewise has a neck portion 32. The portion 32 of the neck and the portion 30 of the work rack is the area in which mounting braces 34 and 35 are aifixed to the work rack. The calibrated rod 36 is firmly attached to the mounting braces 34 and 35. The mechanical variable arm 38 is fastened to the calibrated rod 36 as by a setscrew 39. The mechanical variable arm 38 in FIG. 3 engages a plurality of micro-switches 22, as shown in FIG. 4, at the treatment station and thus communicates the desired current output as explained above with respect to FIG. 2.

Referring to FIGS. 5 through 7 inclusive, in which a further modification of this invention is shown, a work rack 12 has a hanger 14 which engages electrical support is on bus bar arm 10. The electrical current communicated to support 15 is controlled by the electromechanical signaler 40 mounted directly upon bus bar arm 10. The electromechanical signaler 40 has an operating knob 41 with a pointer 42 which passes over index plate 44 carried on the face of the electromechanical signaler 40 for regulating and indicating the current setting. As is shown in FIG. 6, the internal mechanism of electromechanical signaler 40 consists of resistance winding 45 over which wipes a contact 46 connected to rotary knob 41. The output terminals are 48 and 49 respectively, connected to conducting means 50 for communicating the desired current between signaler 40 and wiping terminals 51 connected to the primary current source not shown.

In operation, in the form of the invention illustrated in FIGS. 1 through 4, inclusive, when a particular bus bar arm 10 is carrying a rack or racks 12 having objects of a specific configuration requiring a certain optimum current density, the loader-operator may press the appropriate numbered pin 21 to place the proper resistor 25 in circuit to ensure that the current reaching the rack 12 is the optimum current for that particular work carried by the bus bar arm 10.

The loader-operator controls the setting of the form of the invention shown in FIGS. 3 and 5. And, in accordance with certain aspects of this invention, the rack manufacturer may also control the setting in FIG. 3 by presetting the electromechanical signaler at the time the rack is manufactured.

The operation of the form of the invention shown in FIGS. 5 through 7 inclusive, provides for control by the loader-operator placing the work on the rack in the racking area of a plant, and for a given unit of articles to be racked upon a particular rack at the time the person racking the articles sets the proper index setting for the optimum current to be applied to rack 12 in the various treatment stations.

Accordingly, an arrangement is provided in accordance herewith of a variable control element for individually setting the current for each arm of a plating conveyor in an electrodeposition process. With such an arrangement the optimum current is achieved for the particular objects to be plated which are placed in the racks suspended from each arm. Thus, the different configurations of the objects being plated is determinative of the current directed to them with objects having sharp corners, for example, generally receiving less current and objects with deep recesses more current. In addition, the particular desired optimum current is easily set by the operator-loader at the time of loading of the racks. Furthermore, because the optimum current for the particular objects being plated is individually achieved in accordance herewith, the final cost is reduced simply because objects with different configurations may be plated simultaneously, and because optimum current is always directed for a particular object being plated, there is a substantial reduction in the number of objects imperfectly plated.

While the methods and forms of apparatus herein described constitute preferred embodiments of the invention; it is to be understood that the invention is not limited to these precise methods or forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An apparatus for use in electrodepositing metals onto diversely sized and shaped basis materials exhibiting difiering electrical current characteristics requiring various optimum currents, and having a support, a laterally extending arm disposed on said support, and a work-supporting rack supported by said arm for submersion into a treating vessel therebelow for supporting said basis materials to be plated, and a source of variable current, the combination which comprises a pre-settable calibrated mechanical variator mounted on said laterally extending arm or said work-supporting rack for selectively varying the optimum current in accordance with the size and shape of the particular basis material being plated, means providing flow communication between said source and said rack, and an electrical signaler bias to said variator comprising a variable resistance selectively determined by said variator and connected to said fiow communication means for providing plating current density to basis materials in said rack from said source.

2. Apparatus as described in claim 1 in which said variator is mounted on said arm and in which said signaler is a rheostat having a rotary wiping arm and a circular resistance winding across which said wiping arm rotates to vary resistance across the output leads therefor.

3. Apparatus as described in claim 1 in which said calibrated mechanical variator is a plurality of aligned pins afiixed to said arm, and a set of microswitches disposed adjacent to said pins with said pins arranged to selectively activate said microswitches.

4. Apparatus as described in claim 1 in which said calibrated mechanical variator includes a calibrated rod disposed on said rack, a mechanically variable arm slidingly disposed on said rod, and a set of microswitches disposed adjacent to the path of said arm whereby movement of said arm selectively engages and activates one of said microswitches.

5. Apparatus as described in claim 1 in which said calibrated mechanical variator is disposed on said rack, and said signaler is disposed adjacent thereto.

References Cited UNITED STATES PATENTS 1,412,909 4/1922 Voigt 204-297 2,070,343 2/1937 Turnock 204297 JOHN H. MACK, Primary Examiner S. S. KANTER, Assistant Examiner US. Cl. X.R. 204-228 

